On the dynamics of the Alaska Coastal Current

Abstract

A steady state diagnostic numerical model is used to describe the circulation in the Alaska Coastal Current. The Alaska Coastal Current extends northwards from the Columbia River around the Gulf of Alaska where it becomes a relatively high speed flow. It is characterized by low salinities created by high rates of coastal fresh water discharge. The diagnostic numerical model developed used hydrographic data with spatial resolution of 3.7 km. The results are compared with vertically averaged profiling current meter measurements. The alongshore current components agree quite well while the cross-shelf components occasionally differ not only in magnitude but also in their sign. The model also predicts an increase in the alongshore flow in the offshore regions. This variation is verified by the current meter data. Vertical profiles of the current were compared with the model flows with favorable results in the alongshore direction and a less certain outcome in the offshore flow. While the alongshore flow is well represented by the model, the cross-shelf motion is poorly represented. This could be a contrast between the high speed alongshore flows as compared with the relatively weak cross-shelf flow. The bottom topography also plays an important role in controlling the shelf circulation here.